The potential role of extraocular muscle proprioception in the neural control of eye movements has been obscure. Although the pattern of sensory and motor neuronal innervation of these muscles has been elucidated, relatively little is known regarding the central and peripheral terminations of the extraocular muscle sensory neurones and the types of muscle fibers with which they are associated. The specific aims of the proposed studies are directed toward elucidating the central and peripheral anatomical structures that underlie extraocular muscle sensory innervation in the monkey using light and electron microscopy. The pattern of central synaptic connections of first order muscle sensory neurons will be determined by transganglionic transport of wheat germ agglutinin-conjugated horseradish peroxidase (WGA/HRP). Secondly, these studies will label the sensory nerve terminals with WSA/HRP, transported anterograde from the site of the first order neurons (i.e., semilunar ganglion), in order to inequivocally localize and characterize extraocular muscle sensory receptors. The proposed studies also provide a unique opportunity to examine sensory-motor interactions in the primate oculomotor system. Reciprocal communications between mononeurons and the muscle fibers they innervate serves to maintain the integrity of each of these components of the motor unit. Similarly, trophic interactions may exist between sensory nerve terminals and the particular muscle fiber types with which they are associated. The proposed studies will examine sequential changes in individual exraocular muscle fiber types subsequent to either sensory or motor denervation of the extraocular muscles. Taken together, the proposed studies will begin to define the sensory and motor neuronal interactions that occur peripherally in the oculomotor system. Our long-term goal is to utilize the information obtained from these morhological analyses, combined with the physiological evaluation of functional status using an alert monkey model, in order to comprehend the peripheral changes subsequent to experimentally-induced oculomotor dysfunction.